Sharpening Tojiro DP: suggestions?

Sat Mar 15, 2014 6:17 pm

Hi y'all,

Background:I don't have a lot of sharpening experience, but I have tried about a dozen knives or so a couple of times (months apart) on just two stones. I've managed to get some knives very sharp, and some others (soft German knives) moderately sharp. In short, I can tell my sharpening skills are improving every time I get out my stones, but also that, depending on the knife, I can spend 5-10x longer on one versus another to get the same results. All of my knives have been sharpened from moderately sharp to hair-splitting, using a very cheap 1k-6k combination water stone, so I don't have any experience yet with re-beveling or thinning—all of my work has been matching or steepening factory grinds. Obviously, I want to upgrade stones eventually, but I feel good about learning on the cheap stone first. Any advice to the following can include suggested purchases for a course, 1k, and 4-6k stone (or whatever else). I'm not in to high-polish edges (spray strops, etc.).

Question:One set that eludes me are my Tojiro petty and – especially – pairing knives. They seem to like lower grit finishes and shallow angles best, but other people seem to sharpen this style of knife to high grits and steep angles. (I'd guess my Konos are at ~10-15 degrees and are a breeze to touch up, while the Tojiros, which "feel" half as sharp at best, are probably 20-25 degrees, and frustrate me to all hell on the stones.) I'm wondering what I'm doing wrong. The DPs seem thick behind the edge to me, but I'm not sure what grit I need to thin them, or if this is necessary. Sometimes the cladding makes makes it seem difficult to touch the edge at the angle I want, at least on the label side of the knife, without fear of scratching the cladding above. I'll add that – to my amazement – the tojiros feel screaming, toothy sharp at 1k, but often feel duller after I polish them on the 6k. Am I just missing the angle, do I need a new burr on the 6k, or is the a VG-10 phenomenon? Or perhaps it is unreasonable to expect my petty to feel [almost] as good on a carrot or apple as a gyoto?

Bonus Question:I'm also curious about polishing out the mistakes on my knives. I recently sanded the choil and spine of my masamoto vg with high-grit sandpaper (aluminum oxide, 60 grit). HUGE improvement, but now it looks pretty scratched up on those edges. And admittedly, this knife is my beater knife of sorts and has spent a lot of time in destination kitchens away from home, so it's received other scratches behind the edge along the way. I also managed to barely scratch one of my HDs just above the bevel in a couple places. Do I use metal polish, a 6k or higher stone, or a high-grit sand paper to touch up these blemishes? And what do I do about the labels on this and the Tojiros, which will likely rub off if I polish them? I don't care about the labels per se, but it would be weird for them to run off very unevenly depending on where I have to polish.

I'm NOT at all trying to restore these to "like new" condition, but I'd like to build some techniques for dealing with the steel for general purpose use. If it means removing lots of steel, I guess I'd just let them be, but if this is purely cosmetic work, it seems worth it to get them looking as nice as can be.

Any and all suggestions are welcome, including links to the many postings that I have probably missed that already deal with these issues!

Re: Sharpening Tojiro DP: suggestions?

Sat Mar 15, 2014 6:46 pm

Sounds to me like thinning is in order. With thinning you will be grinding some of that cladding behind the edge down and allowing you a more acute angle on your edges.

As far as the DPs vs the Konos, the VG10 steel in the DPs has a reputation for stubborn burrs. It may be a question of using decreasing pressure and trailing strokes to gently abrade the final burr. One test that might be useful is to use a synthetic cork to deburr the edge. Just lightly draw the edge into the cork. This will tear off any remaining burr. In theory, you would prefer to abrade the burr not tear it off. In practice many people deburr this way and get decent enough edges. I aim not to need this step, but as a diagnostic tool, if the edge improves after deburring this way, then burr was your problem and now you know what to work on.

Furthermore, the steel in the DP is unlikely to take as fine an edge as the steel in the Kono, however, you should not write off the DP on this account. The difference between the steels, in terms of refinement, is somewhat marginal. I have not worked with the HD steel in the Kono, but I speculate that the DP will take comparatively more effort to get the same degree of sharpness as the Kono. The DP can take a reasonably refined edge, I usually take my DP gyuto to 6k.

Looking ahead to future stone purchases, you might consider filling in the middle range of your progression some. I like to have a 2-3x increase in grit between stones. So a 500, 1k, 2k, 4k, 8k, or a 300, 1k, 3k, 6k progression are what I aim for. It is my opinion, that going from 1k to 6k, though commonly done, is more difficult than many people realize. It takes a lot of work on the 6k stone to polish away the scratches left by the 1k stone. The addition of a 2k or 3k in between makes sharpening a lot easier.

As far as cosmetic work. Per a recommendation by Tim Johnson (Taz here), I have used a progression of Scotch-Brite pads to sand/polish out some scratches. I have not tried it on a mono-steel knife like your Kono, but I did do it on my Tojiro DP gyuto. I ended up removing the logo entirely with little effort, so that should answer that question . The finish is not like the factory finish, but it is a nice look. I finished with about a pad that was a 0000 steel wool equivalent, and the finish is reflective enough that I can identify shapes reflected in the surface but it is not quite a mirror finish. I think something like Flitz would pretty much get me to a mirror finish. The cladding on the DP is very soft and abrades quickly and easily. The Kono would likely be harder, abrade slower, and I would hesitate to advise what the finish would be like without having tried it.

Re: Sharpening Tojiro DP: suggestions?

Sat Mar 15, 2014 7:24 pm

cederhouse:

First off: I was just admiring your collection earlier today! (I checked out the collection pics Mark requested for the first time.) Thanks for the comments. I noticed some chatter about the pads previously. By "scotch bright," I'm assuming that you mean steel wool and not the nylon pads? Or do you actually use different "grades" of scotch bright nylon (and if so, how do you tell?)

More than this, your comment about the intermediate stone between 1k and 6k is very telling. I've noticed that this gap is actually a serious issue as I get a better feel for sharpening, and when I buy new stones, I will likely close it by moving up and down (1.5k and 4k, for example), since I don't need a 6k polish for home and like a slightly toothier edge most of the time, anyway. That said, more and more, I am seeing the advantage of having more stones, despite the constant comments against this by people like Murray Carter, and despite the fact that I'm not trying to get as high as 8k or 10k. Everything seems easier and faster with more stones when watching videos of others.

As for thinning the DP: what is the best way of doing this, and can I do a good job of it with the 1k? Is the best thing to just find some contact behind the edge, stick too it, and grind away until I create a secondary bevel? Or should I roll the knife a bit to try to maintain the convex grind, even behind the tip? Thinning perplexes me: it seems easy when the knife already has a pronounced secondary bevel (just follow the grind), but I'm lost with other grinds like the DP's. I guess this is where experience kicks in (or lack thereof). I've also noticed (or felt) that the grind on the DPs are not 50/50 (the pairing looks/feels closer to 70/30, where the back is ground flat, and the front has more of a convex; the petty is similar, but more like 60/40). I don't even know if this is true, but if feels true. In this case, I assume that an asymmetrical thinning will be appropriate. Finally, will the thinning make the knife look really scratched? Will following with the 6k fix this, or will I need to polish behind the edge to get it looking normal again? Last time I tried, I actually got scared and stopped because the stone was leaving dark grey buffs higher on the cladding when I tried to go too thin (or too high).

And for all: is a 300-500 grit stone coarse enough for tip repair? I have a very, very minor tip chip on the masamoto that I want to attack, but I'm a bit scared to do it with the 1k, for fear of pressing too hard or moving too aggressively and damaging the knife or – or likely – gashing the stone with such repetitive work on a tip. I was amazed at Melampus's repair work ( kanji-id-t1281.html ) and was wondering just what it takes to do that kind of reshaping! His first two stones were 160 and 600...but can more minor tip and bevel work be done with a 320-500 grit?

Sorry for the long post(a). I appreciate the feedback, and partial responses!

Re: Sharpening Tojiro DP: suggestions?

Sat Mar 15, 2014 10:06 pm

1) If you go to the hardware store, there are abrasive pads sold next to the steel wool, that is what you are looking for. They are color coded and IIRC have a steel wool equivalence listed. My advise is google the a color coded table so you know which you are looking at, but the verbal description will get you close.

2) I think you can get a good edge with pretty much any stone combination, but having a progression where your coarser stones segue well with the finer stones makes for less effort on your part. Using less effort is not merely a question of being easier, sharpening uses fine motor skills which fatigue kills. It should be said that some stones have wider reaches than others. My 4k and 6k Kings struggled to refine my Nubatama 1k stone. I recently added a 2k Nubatama Ume and a 6k Arashiyama and this progression works better.

3) I do not have enough experience with thinning to offer a lot of detailed advice here, but FWIWa. If you are sharpening at ~15° per side, a basic job of thinning would hit only the area directly behind the edge by rolling down to ~10° or so. This will ease the transition between your bevel and the blade making it perform like a thinner knife. Search YouTube for knife thinning, there are a number of videos on this subject. b. A 1k stone would probably be a good place to start. Removing metal quickly with a coarser stone is nice, but for a first go at it moving slower might be helpful. c. You can try to impart a convexity to your thinning job if you like, I have seen videos of people doing this. Just remember, when hand sharpening, you will impart a subtle convexity to your work just with minute wobble of knife within your grip, so don't overdo it.d. You can thin aggressively high into the grind, even all the way up the blade, I have never done this on a knife (a few axes). This is where experience and power tools become nice. e. There may be scratching from two causes. One the stone will leave scratches where ever it touches. These you can polish out with the finer stones in your progression. Aesthetically it looks like your bevel is elongated up the blade some. There may be some aesthetic issues with the cladding where the scratch patter will look different. Here is where you can polish up the cladding with the Scotch-Brite pads. The other cause of scratching is errant contact with the stone or swarf and stone slurry working up onto the blade and scratching it. This can be limited by working carefully and by rinsing the blade with water BEFORE wiping with a rag. Again this can be polished out with the pads.

4) I just looked at my DP 240mm gyuto and to my eye I cannot see any asymmetry to the grind. The bevels are often a little off one way or the other from the factory, but can be adjusted pretty easily.

5) Depending on where the tip chip is there are a few ways to tackle it. Check this video out and see if this address part of your question: http://www.youtube.com/watch?v=gFBuOBarMFk. To limit damage to the stone surface, use the side of the stone. If the chip is in the edge, but not all the way out on the tip, you can sharpen normally until you work back past the chip. With a 1k stone this will take a while.

Re: Sharpening Tojiro DP: suggestions?

Re: Sharpening Tojiro DP: suggestions?

Sun Mar 16, 2014 10:46 am

I have a tojiro dp gyuto just like you. I've found this knife to be pretty amazing in terms of how sharp it can get. I also have the goko hammered damascus with 19c27 and the tojiro VG10 attains a similar edge. I have not tried carbons yet although my first carbon knife is on its way as I write this.

The tojiro is sharp ootb but I found that it chipped easily. I suspect they had put a less than 30 degree edge on it giving you that wow factor ootb but not necessarily holding it for long. After a few sharpenings bringing the edge up to around 30 degrees, it seems to be holding an edge for a decent amount of time and no chipping even though I do a lot of chopping with the blade banging directly on a poly board. Quite amazingly there is very little curling from use also so at this time the tojiro vg10 holds its own.

I've not found it to burr tenaciously either. One thing I do to deburr is to draw it through a cork and run it a few times on a ceramic rod. That treatment on the ceramic rod deburrs the edge nicely for the next grit. I find using the rod allows me to very specifically remove very fine stubborn burrs when I'm close to moving to stropping.

I suspect your finding the 6K to blunt the knife could be due to what many have mentioned earlier when you use both edge leading and edge trailing strokes on the 6K side of your stone. The 6K stone may be quite soft and when you push with an edge leading stroke you unintentionally push the edge into the stone cutting the stone and rounding your edge. Use edge trailing strokes on the 6K side to polish the edge and then finish on a strop.

My routine is 600 and 1200 grit DMT plate, I didn't want to deal with flattening stones but I just ordered the green brick to incorporate a stone into the routine. Deburr with ceramic rod in between and after plates. Then 3 micron strop on balsa, and 1 micron diamond on balsa to finish, if I want to refine it further I use a bare horse butt strop but find that unnecessary for general use. Push cuts paper from an inch away and cuts tomato skin with no sawing or crushing.

Re: Sharpening Tojiro DP: suggestions?

Sun Mar 16, 2014 3:11 pm

Thanks for the very thorough and helpful post(s), guys. Cedarhouse—this is terrific, and Rayong, your experiences also help put things in perspective, for sure.

Lots of these tips are things I've come across before, but without any reason to sharpen or repair more than every few months, I forget the stuff (watching all the videos in the world doesn't help me without hand-on practice to help me remember)! All of the pad stuff is new, and I think this will be extremely helpful for the kind of work that I am most uneducated about: rounding and cosmetic finishing of edges and surfaces. I think there are less videos (and certainly less good ones) of these kinds of procedures—for example, Mark's video that you link describes the basics of outlining and grinding a new tip from the spine, but it doesn't give any sense on how one rounds, blends and polishes the new spine/tip (not that it should, I'm just saying that these details are often left out). It also doesn't give a sense of potentially re-profiling the edge from the edge side, which is probably easier in some cases. Another quick search on chips brings up Murray Carter, who spends two videos describing a repairing some chips, but then only mentions how one could finish by reshaping the secondary bevel, without doing this himself. (I have watched other videos of his on thinning a knife, but again, questions remained.) My point is that all of these videos are helpful, but the great thing about this forum is that people can address more specific questions rather than just describing a process that is already second nature to them! (I know all-to-well from teaching that it is easy to summarize a difficult concept or procedure, or to realize your students are still in the dark because you forgot to address the most basic issues!)

I am still left with one basic question: if a 1k "scratches," and a 6k removes the scratches, at what grit level does a stone generally switch from producing obvious scratches to producing something more like a polished surface; and again, at what grit level does one switch from generally polishing (a dull finish, like say the side of a Wustof) to something like a mirror finish? I feel like I get mirror finishes on my edges from just 6k, but I hesitate to rub the whole side of a knife against a 6k to try to get it such a polish—it seems like a fine-grain stainless polish would be better for such things, and I don't really remember seeing or hearing anyone talking about polishing their knives in this way with stones. Is this the idea behind Flitz? (Bar Keepers, which I've tried, doesn't seem to do much for small scratches, although perhaps I wasn't rubbing hard enough, or with the proper scrubber.)

Re: Sharpening Tojiro DP: suggestions?

Sun Mar 16, 2014 4:00 pm

You don't need to thin the knife or polish it by rubbing the entire side against the 6k stone. Chances are you're not going to get an even finish that way. If you want to polish the side of the knife use some metal polish. Just thin the shoulder and sharpen the edge. Work on keeping your hand steady when sharpening.

Re: Sharpening Tojiro DP: suggestions?

Sun Mar 16, 2014 9:49 pm

Salem,

I don't know that there is a good answer to your final question. For scratches on the side of the blade, use the pad progression to the highest grit available then try using flitz or something like that. You would not want to polish the sides of the blade using the stones. Barkeepers Friend is mildly abrasive, but what it excels at is chemically removing oxidation.

Under sufficient magnification the surface will always be scratched. To the naked eye the 6-8k range is probably where you start getting close to mirrored. Since grit ratings are not standard, this is not as useful as you might hope. I am guessing that is around the 1-2 micron range. To get an idea of the abrasive size range check out the chart at the top of this thread: the-grand-unified-grit-chart-t592.html.